JEE Main 2022 · 26 July · evening · Single correct · +4 / −1
The correct decreasing order of priority of functional groups in naming an organic Question: compound as per IUPAC system of nomenclature is
- (a) -COOH>-CONH₂>-COCl>-CHO
- (b) SO₃H>-COCl>-CONH₂>-CN
- (c) -COOR > -COCl > -NH₂ > ⟩ C=O
- (d) -COOH>-COOR>-CONH₂>-COCl
Answer and solution
Answer (b) SO₃H>-COCl>-CONH₂>-CN
Solution
Chemistry ma’am · 3 steps
Write the full priority ladder once, then look for the one pair each option puts in the wrong order.
- The priority ladder. IUPAC ranks the carboxylic acid at the top, then sulphonic acid, then the acid derivatives, then nitrile, aldehyde, ketone, alcohol and amine.
-COOH > -SO₃H > anhydride > -COOR > -COCl > -CONH₂ > -CN > -CHO > C=O > -OH > -NH₂
- Check each option. An option is correct only if every group in it sits in the same relative order as on the ladder. It does not need to list every group.
Option Pair to check Verdict (a) -CONH₂ placed above -COCl wrong: acid halide outranks amide (b) -SO₃H > -COCl > -CONH₂ > -CN every pair matches the ladder (c) -NH₂ placed above C=O wrong: ketone outranks amine (d) -CONH₂ placed above -COCl wrong: acid halide outranks amide - So. Only (b) keeps the correct decreasing order: sulphonic acid, then acid chloride, then amide, then nitrile.
The idea to keep. Acid first, then its derivatives as anhydride, ester, acid halide, amide. After them come nitrile, aldehyde, ketone, alcohol, amine. Learn this ladder once and each option check takes seconds.
Answer from the NTA final answer key. Solution by PrepWiser.